In fact, this commandment was not specifically changed. The others which were changed to suit the needs of the pigs, were:
'No animal shall sleep in a bed', which was adjusted to, 'No animal shall sleep in a bed with sheets,' after the pigs had moved into the farmhouse and slept in beds, and 'No animal shall kill any other animal,' was altered to 'No animal shall kill any other animal without cause.' This change was made after a large number of animals had been executed by Napoleon's dogs for confessing that they were traitors and spies.
Another commandment which was changed is, 'No animal shall drink alcohol,' to 'No animal shall drink alcohol to excess,' once the pigs had taken to drinking copious quantities of beer and whisky. The pigs also adapted the maxim, 'Four legs good, two legs bad,' to 'Four legs good, two legs better,' when they took to walking on their hind legs and carrying whips in their trotters.
It was not long after this specific adjustment had been made that the pigs erased all the commandments and replaced them with a single nonsensical one on the wall of the big barn, which read:
'All animals are equal, but some animals are more equal than others.'
Once this senseless and illogical statement had been put up, it was not strange for the animals to see the pigs adopting human behaviour and characteristics. The pigs bought a wireless, installed a telephone and took out subscriptions to magazines and newspapers.
It was only at this point that the pigs started wearing clothes:
Napoleon himself appearing in a black coat, ratcatcher breeches, and leather leggings, while his favourite sow appeared in the watered silk dress which Mrs. Jones had been used to wearing on Sundays.
it is clear that things on the farm had, ironically, gone full circle. The only difference now was that the other animals were now ruled and enslaved by their own kind and their masters had, indeed, become almost human themselves, as it is so aptly put in the last sentence of the novel:
The creatures outside looked from pig to man, and from man to pig, and from pig to man again; but already it was impossible to say which was which.